I won't write anything about this study, just posting the url for you that may find it interesting or wonder how they got PD as I do. These scientific papers are above my understanding except for their summaries that are written for us dummies.

From personal lifetime experiences I agree whole heartedly it comes from the gut. I don't have a sign on to that website. When I click on your link it takes me to the login page. But I've done a ton of research and like I said I definitely agree. Thanks and be well. Judy

Parkinson's disease is strongly linked to the degeneration of the brain's movement center. In the last decade, the question of where the disease begins has led researchers to a different part of the human anatomy. In 2003, the German neuropathologist Heiko Braak presented a theory suggesting that the disease begins in the gut and spreads to the brain. The idea has since, despite vocal critics, gained a lot of ground. Researchers at Lund University in Sweden now present the first direct evidence that the disease can actually migrate from the gut to the brain.

I am familiar with Braak's 'Dual Hit Hypothesis' and he specifically mentions a virus as a probable pathogen to start the process:

Parkinson's disease: a dual-hit hypothesis.

"We propose that a neurotropic pathogen, probably viral, enters the brain via two routes: (i) nasal, with anterograde progression into the temporal lobe; and (ii) gastric, secondary to swallowing of nasal secretions in saliva."

PD is genetically related to tuberculosis, leprosy and Crohn's disease. The first 2 have confirmed mycobacterial origins and in CD the putative cause is Mycobacterium avium subspecies paratuberculosis, aka... paratuberculosis or MAP.

Nocardia asteroides and rhodococcus aurantiacus, both closely related to mycobacterim tuberculosis, caused parkinsonism in lab animals which was relieved with L-dopa. There have been cases of tuberculosis-induced parkinsonism which was cured with antibiotics.

Yes Braak's hypothesis is a good one but he, like many scientists, have their particular bias and to only state 'viral' is a narrowing of the possibilities.